The control of hemorrhage (bleeding) is a critical step in first aid and field trauma care. Unfortunately, the occurrence of excessive bleeding or fatal hemorrhage from an accessible site is not uncommon. (J. M. Rocko et al. (1982). J. Trauma 22:635). Mortality data from the Vietnam War indicates that 10% of combat deaths were due to uncontrolled extremity hemorrhage. Up to one third of the deaths from exsanguination during the Vietnam War could have been prevented by the use of effective field hemorrhage control methods. (SAS/STAT Users Guide, 4th ed. (Cary, N.C.: SAS Institute Inc; 1990)).
Although civilian trauma mortality statistics do not provide exact numbers for prehospital deaths from extremity hemorrhage, case and anecdotal reports indicate similar occurrences (J. M. Rocko et al. (1982). J. Trauma 22:635). These data suggest that a substantial increase in survival can be effected by the prehospital use of a simple and effective method of hemorrhage control. Unfortunately, such a method has not been successfully demonstrated by use of commercially available hemostatic devices.
Most successful high-pressure hemostatic devices currently on the market are nominally, if at all adhesive. Good examples of such devices are the QuikClot® ACS™ (Z-Medica, Wallington, Conn.) and HemCon™ bandage (HemCon, Portland, Oreg.), the two hemostatic devices currently supplied to members of the US armed forces. The mineral zeolite crystals in the QuikClot sponge cause adsorption of the water molecules in the blood, thus concentrating the clotting factors and accelerating blood clotting. The chitosan mixture that makes up the HemCon bandage has a positive charge and attracts red blood cells, which have a negative charge. The red blood cells are drawn into the dressing, forming a seal over the wound, and stabilizing the wound surface.
The HemCon bandage product mentioned above was developed in an attempt to provide pre-hospital hemorrhage control and has already demonstrated limited success in the field. However, the chitosan network that makes up the HemCon bandage can be saturated with blood and fail quickly when faced with brisk flood flow or after 1-2 hours when confronted with moderate blood flow from a wound (B. S Kheirabadi et al. (2005). J. Trauma. 59:25-35; A. E. Pusateri et al. (2006). J. Trauma. 60:674-682). Also, the HemCon bandage patch is available only as a stiff patch that cannot fit easily into irregular wounds, further limiting its utility.
Other polysaccharide-based hemostatic devices that have been suggested for use in hemorrhage control are RDH™ (Acetyl Glucosamine), TraumaDEX™ (MPH), Chitoskin™ (Chitosan & Gelatin), Celox™ (Chitosan Crystals). However, none of these types of bandage have been able to consistently demonstrate sufficient ability to not fail in the face of significant blood flow. As such, they may be considered more appropriate for post-medical care wound management than for emergency trauma care.
QuikClot ACS™, also mentioned above, has also demonstrated efficacy in staunching moderate levels of hemorrhage. However, the water adsorption mechanism of mineral zeolite cannot be effected without the release of a large amount of heat. As such, application of the QuikClot ACS™ results in high temperatures and severe burns at the injury site, which damage surrounding tissue areas and make later medical care far more complicated (A. E. Pusateri et al. (2006). J. Trauma. 60:674-682). Clearly, a hemostatic solution without this significant side effect is more ideal. While QuikClot has developed a mineral mixture that releases less heat upon application, the efficacy of the cooler mixture is insufficient for serious trauma care. Furthermore, neither the original nor cooler mineral mixtures can stop brisk arterial bleeding.
Hemostatic bandages which are adhesive in nature are known in the art, yet have many complications and drawbacks to their use. For example, the widespread hemostatic use of fibrinogen and thrombin was common in the last year of World War II, but was abandoned because of the transmission of hepatitis (D. B. Kendrick, Blood Program in WW II (Washington, D.C.: Office of the Surgeon General, Department of Army; 1989), 363-368).
Fibrinogen dressings were first used by trauma surgeons during World War I when Grey and his colleagues made prepolymerized fibrin sheets and powders. During World War II, fibrin glue was created with prepolymerized Styrofoam-like sheets of fibrin and fibrin films by the United States military and the American Red Cross. Fibrin based dressings show a significant difference in controlling bleeding time and reducing blood loss when compared to a control. (Jackson, M., et al. (1996). J. of Surg. Res. 60:15-22; and Jackson, M., et al. (1997). Surg. Forum. XL, VIII:770-772)
Despite the efficacy of fibrinogen dressings in controlling hemorrhage, the use of fibrinogen dressings was discontinued as blood and serum borne diseases such as hepatitis and HIV were often transmitted since the dressings comprised purified human or animal fibrinogen or other purified blood products. (Holcomb, J. B., et al. (1997). Surgical Clinics of North America. 77:943-952)
In the past few years, however, there has been a renewed interest in fibrin based products for treating wounds as plasma purification techniques have nearly eliminated the risk of blood and serum borne diseases.
A hemostatic sandwich dressing has been described by the US Red Cross, which contains a layer of thrombin sandwiched between layers of fibrinogen (see, e.g., PCT/US99/10952, U.S. Pat. Nos. 6,054,122, 6,762,336). That hemostatic dressing has demonstrated much success in treating potentially fatal trauma wounds (E. M. Acheson. (2005). J. Trauma. 59(4):865-74; discussion 874-5; B. S. Kheirabadi. (2005). J. Trauma. 59(1):25-34; discussion 34-5; A. E. Pusateri. (2004). J. Biomed. Mater. Res. B Appl. Biomater. 15; 70(1):114-21) In fact, in those porcine studies, the fibrin sandwich dressing greatly outperformed the HemCon and QuikClot products in treating potentially fatal trauma wounds, demonstrating a>75% survival rate after 2 hours, versus 0% survival when the standard army field bandage, HemCon bandage, or QuikClot powder was used.
Although such dressings can be used in methods for treating wounded tissue, such conventional sandwich dressings can become delaminated, whereby the edges of the layers of the dressing no longer adhere to each other. Such delamination can result in reduced interaction of the dressing components layers, with decreased effectiveness of the dressing in preventing hemorrhage.
An improved fibrin-based hemostatic sandwich dressing has been described which comprises a plurality of layers that contain resorbable materials and/or coagulation proteins. Specifically, the dressing (see PCT/US03/28100, U.S. patent application Ser. No. 0060/155,234) includes a layer of thrombin sandwiched between a first and second layer of fibrinogen, wherein the layer of thrombin is not coextensive with the first and/or second layer of fibrinogen.
Despite the advances in fibrin wounds dressings, these bandages suffer from many drawbacks. The lyophilized fibrinogen used to make the bandage must be purified from human blood plasma. As this is a costly and delicate procedure, the resulting fibrinogen bandage is extremely expensive to produce and only has a very short shelf life at room temperature. The more fibrinogen that is added to the backing, the better the bandage works in stopping bleeding. However, the more fibrinogen added to the backing, the more costly the bandage. Additionally, high amounts of fibrinogen on the bandage backing may contribute to the fragility of the bandage, making it crumbly and difficult to work with. As a result of these limitations, no efficacious fibrin bandage is commercially available.
Thus, while an advanced fibrin dressing could control hemorrhage without significant side effects and fill the previously mentioned deficiency in active trauma care hemostasis, price and stability limitations prevent any such dressing from becoming commercially viable and being distributed into the field.
Liquid fibrin sealants or glues have been used for many years as an operating room adjunct to hemorrhage control (J. L. Garza et al. (1990). J. Trauma. 30:512-513; H. B. Kram et al. (1990). J. Trauma. 30:97-101; M. G. Ochsner et al. (1990). J. Trauma. 30:884-887; T. L. Matthew et al. (1990). Ann. Thorac. Surg. 50:40-44; H. Jakob et al. (1984). J. Vasc. Surg. 1:171-180). Also, single donor fibrin sealants have also been widely used clinically in various surgical situations. (W. D. Spotnitz. (1995). Thromb. Haemost. 74:482-485; R. Lerner et al. (1990). J. Surg. Res. 48:165-181)
While a number of absorbable surgical hemostats are currently used in the surgical arena, no existing product is sufficiently strong to provide the mechanical and biological support necessary to control severe hemorrhage.
Currently available hemostatic bandages such as collagen wound dressings (INSTAT™, Ethicon, Somerville, N.J., and AVITENE™, C R Bard, Murray Hill, N.J.) or dry fibrin thrombin wound dressings (TACHOCOMB™, Hafslund Nycomed Pharma, Linz, Austria) are restricted to use in surgical applications, and are not sufficiently resistant to dissolution in high blood flow. They also do not possess enough adhesive properties to serve any practical purpose in the stanching of severe blood flow. These currently available surgical hemostatic bandages are also delicate and thus prone to failure should they be damaged by bending or loading with pressure. They are also susceptible to dissolution in hemorrhagic bleeding. Such dissolution and collapse of these bandages may be catastrophic, because it can produce a loss of adhesion to the wound and allow bleeding to continue unabated.
Arterial bleeding is also not manageable with the application of oxidized cellulose (SURGICEL, Ethicon, Somerville, N.J.) or gelatin sponge (SURGIFOAM, Ethicon, Somerville, N.J.) absorbable hemostats. These products are intended to control low-pressure bleeding from bone and epidural venous oozing. Gelatin sponges are not appropriate for high-pressure, brisk flowing arterial bleeding because they do not form a tight bond with the source of bleeding and are thus easily dislodged. Oxidized cellulose is also not appropriate for controlling arterial bleeding because it swells and needs to be removed from the application site when hemostasis is achieved. When the blood flow is too high, too much swelling occurs before hemostasis can be achieved (M. Sabel et al. (2004). Eur. Spine J. 13(1):S97-101).
The most widely used tissue adhesives are generally unfit for use as hemostatic devices, for reasons generally related to inability to be easily prepared and applied in the field. A good example of this is the cyanoacrylate family of topical skin adhesives, such as Dermabond™, Indermil™, Liquiband™ etc. The nature of cyanoacrylate's rapid activation when exposed to air and cyanoacrylate's inability to bind to wet surfaces make cyanoacrylate-based products inappropriate for use in an active hemostatic field dressing.
Gelatin has been used in a variety of wound dressings. Since gelatin gels have a relatively low melting point, they are not very stable at body temperature. Therefore, it is imperative to stabilize these gels by establishing cross-links between the protein chains. In practice, this is usually obtained by treating the gelatin with glutaraldehyde or formaldehyde. Thus, cross-linked gelatin may be fabricated into dry sponges which are useful for inducing hemostasis in bleeding wounds. Commercially available examples of such sponges include Spongostan (Ferrosan, Denmark), Gelfoam (Upjohn, USA), and Surgifoam (Ethicon. Somerville, N.J.). A major disadvantage of these sponges is that the cross-linking agent used (formaldehyde or glutaraldehyde) is toxic for cells. The negative effect of glutaraldehyde cross-linking is exemplified, for instance, by the findings of de Vries et al (Abstract Book of the Second Annual Meeting of the WHS, Richmond, USA, p 51, 1992). These authors showed that glutaraldehyde cross-linked collagen lattices were toxic for cells, whereas the non cross-linked variety was not. Therefore, despite their beneficial hemostatic properties, these products are not very optimal as wound dressings for the treatment of problematic wounds. Consequently, a gelatin-based wound dressing which uses a different, less toxic, cross-linking technology would be very desirable.
Aside from potential toxicity, gelatin networks alone do not provide the mechanical properties necessary for controlling brisk bleeding. They are more appropriate for wound management applications that only require a small amount of fluid absorption. In one study, it was concluded that sheets of glutaraldehyde cross-linked gelatin are more appropriate as a dressing for sustained wound healing, particularly of dystrophic tissue which need longer time. Alternatively, they may be useful as a scaffold for cell attachment, where they can stimulate a poorly reactive microenvironment throughout prolonged in situ presence (M G Tucci. (2001). J. Bioactive & Comp. Polymers. 16(2): 145-157).
Gelatin networks cross-linked with polysaccharides have also been suggested for use in controlling bleeding. These hemostatic compounds are unhindered by the potential toxicity of glutaraldehyde cross-linked gelatin sponges. However, the gelatin-polysaccharide substances generally lack mechanical strength and are intended mainly to control small amounts of oozing fluid during surgery or to limit wound oozing over an extended, post-medical care period.
One example of a gelatin-polysaccharide compound is a gelatin-alginate wound dressing that is cross-linked in situ. Such a dressing has no adhesive function and is mainly used to hold in moisture on the wound site. The dressing swells to 90% of its initial size, which greatly reduces its mechanical strength (B Balakrishnan et al. (2005). Biomaterials. 26(32):6335-42).
Another, more widespread example, is a cross-linked gelatin-chitosan wound dressing (examples in U.S. Pat. Nos. 6,509,039, 4,572,906). While some have suggested the use of such dressings for trauma care (Chitoskin™), the hemostatic properties of this material are simply insufficient to control high-pressure bleeding. Also, the material swells significantly when confronted with high volumes of bodily fluids. Such dressings are more appropriate for treating chronic wounds and burns.
Yet another example is mentioned (U.S. Pat. No. 6,132,759) where solubilized gelatin is cross-linked with oxidized dextran. This material is suggested for the covering and long-term treatment of wounds since it demonstrated a high absorptive capacity and favorable controlled release properties for the delivery of therapeutic substances, particularly to wounds.
Currently no material involving cross-linked gelatin networks or networks of other materials cross-linked with gelatin has been able to independently provide hemostasis for brisk internal bleeding. As such, thrombin is frequently added to gelatin matrices to enhance the hemostatic capacity. However, this is only able to increase the hemostatic capacity of gelatin moderately. A study was done comparing the hemostatic capacity of FloSeal gelatin matrix (BioSurgery, Fremont, Calif.) and GelFoam gelatin matrix soaked in active thrombin solution. Aside from the problem caused by antibody responses to thrombin in 3% of patients, neither enhanced hemostatic device was able to stop flow characterized bleed in more than ⅔ of patients after 5 minutes. Pulsatile arterial bleeding is far more brisk than flow bleeding and would most certainly present a problem for these thrombin-soaked matrices (F A Weaver et al. (2002). Ann. Vasc. Surg. 16(3):286-93).
In any case, there remains a distinct deficiency in trauma care of a novel, active hemostatic field dressing that can control hemorrhage without significant side effects.